1) What is the concentration of the drug in the bloodstream at t = 8 hours?

Question

When a certain prescription drug is taken orally by an adult, the amount of the drug (in mg/L) in the bloodstream at t hours is given by the function y = f(t) shown in the graph.

Answer 1

The function f(t) was not provided in the question. Anyway, you want f(8), so plug t=8 into f(t) and evaluate. If all you have is a graph without an expression for f(t), then find t=8 on the horizontal axis and move vertically up until you intersect the curve, then move horizontally left until you reach the vertical axis, and read the value of f(8) at the intersection with the vertical axis.